The present invention generally relates to a rear toe control system and method, and more particularly relates to a rear toe control system and method that imposes a speed limit on a vehicle during failure of the rear toe control system.
A rear toe control (RTC) system is known that can individually vary the toe angles of the right and left rear wheels on a vehicle. In particular, the toe-in and toe-out of the rear wheels can be freely controlled when desired by simultaneously actuating right and left actuators in a symmetric manner. If one of the right and left actuators is extended while the other is retracted, the two rear wheels may be steered either in the right or left direction. A target toe angle can be calculated for each rear wheel based on a steering angle of the steering wheel of the vehicle and from a vehicle speed of the vehicle. Additionally, while feeding back the output (actual toe position) from each toe-angle sensor (i.e., position sensors), an optimum torque that should be produced from the corresponding actuator can be computed from the deviation of the actual toe angle from a target toe angle, and an electric motor can be controlled so as to produce the optimum torque through a current feedback loop.
In one known rear toe control system, at least one of the toe-angle actuators can be actuated to make the toe angles of the two wheels agree with one another when a fault of the rear toe control system is detected. When one of the wheels has become fixed in position without regard to a control signal supplied to the corresponding actuator, the actuator for the other wheel can be actuated so as to make the toe angles of the two wheels equal to each other. When at least one of the toe-angle sensors is found faulty, the actuators can be both actuated until the actuators reach positions corresponding to limit stoppers. When information for determining target values of the toe angles of the right and left wheels is found faulty, the actuators can be both actuated until the actuators reach positions corresponding to prescribed referenced toe positions. In another known system, the allowed speed for a vehicle is searched via a look-up map under certain failure conditions of the RTC system.